The present invention generally relates to fuel supplying systems for fuel supplying apparatuses having a preset fuel supplying capability, and more particularly to a fuel supplying system which corrects an error in a fuel supplying quantity which inevitably occurs when carrying out two successive fuel supplying operations in different fuel supplying modes such as a preset fuel supplying mode and a normal fuel supplying mode, so that an accurate fuel supplying operation can be carried out regardless of the fuel supplying mode.
Conventionally, there is a fuel supplying apparatus capable of carrying out a preset fuel supplying operation. According to this fuel supplying apparatus, a desired fuel supplying quantity or price is preset, and a predetermined fuel supplying operation is carried out to supply fuel corresponding to the preset fuel supplying quantity or price. Generally, such a fuel supplying apparatus comprises a pump, a flowmeter, a fuel supplying nozzle, a flow quantity generator, an indicator, a preset switch, and a fuel supply stopping means. The pump is provided at an intermediate part of a pipe arrangement which has one end thereof communicating to a tank. The fuel supplying nozzle is connected to the other end of the pipe arrangement through a fuel supplying hose. The flow quantity generator generates a flow quantity signal in correspondence with the quantity of fuel measured in the flowmeter. The indicator indicates the quantity of supplied fuel based on the flow quantity signal generated from the flow quantity generator. The preset switch is used to preset the desired fuel supplying quantity during a preset fuel supplying mode. The fuel supply stopping means stops the supply of fuel from the fuel supplying nozzle when the quantity of supplied fuel reaches the preset fuel supplying quantity which has been preset by the preset switch. The fuel supply stopping means is constituted by a motor which is provided for driving the pump, or by a stop valve or the like which is provided in the pipe arrangement.
During a normal fuel supplying operation, the starting and stopping of the fuel supply is performed by opening and closing a valve of the fuel supplying nozzle. On the other hand, during the preset fuel supplying operation, the start of the fuel supply is performd by opening the valve of the fuel supplying nozzle, but the stopping of the fuel supply is performed by the fuel supply stopping means. In other words, the fuel supply is stopped during the present fuel supplying operation by stopping the motor which drives the pump or by closing the stop valve provided in the pipe arrangement, for example. Further, the valve of the fuel supplying nozzle is operated after the preset fuel supplying operation is completed. For this reason, the valve of the fuel supplying nozzle remains open even when the fuel supply stopping means stops during the preset fuel supplying operation, and a part of the fuel within the pipe arrangement between the fuel supply stopping means and the fuel supplying nozzle and within the hose will flow into a fuel tank of a vehicle. The quantity of fuel which flows into the fuel tank of the vehicle in this manner after the actual preset fuel supplying operation is completed, depends on the length of the pipe arrangement and the hose, and differs for each fuel supplying station. Normally, this quantity of fuel is in the range of 0.1 liters to 0.5 liters. For example, in a case where the mode with which the fuel supplying operation is to be carried out differs between two successive fuel supplying operations, such as a case where a previous fuel supplying operation is carried out in the preset fuel supplying mode and the fuel supplying operation is now to be carried out in the normal fuel supplying mode, a small error is introduced in the actual quantity of fuel which is supplied.
In other words in a case where the fuel supplying operation is carried out in the normal fuel supplying mode for two successive fuel supplying operations, the quantity of fuel supplied during one fuel supplying operation is equal to the quantity of fuel supplied from a time when the valve of the fuel supplying nozzle is opened up to a time when the valve of the fuel supplying nozzle is closed, and the actual quantities of supplied fuel indicated on the indicator are the same for the two successive fuel supplying operations. On the other hand, when the previous fuel supplying operation is carried out in the preset fuel supplying mode and the fuel supplying operation is now to be carried out in the normal fuel supplying mode, the quantity of fuel which is required to fill a part of the pipe arrangement and the hose which become empty at the time when the previous preset fuel supplying operation is completed, by driving the pump when starting the fuel supplying operation in the normal fuel supplying mode, will be measured in the flowmeter before the valve of the fuel supplying nozzle is opened. Accordingly, the actual quantity of fuel which is supplied from the time when the valve of the fuel supplying nozzle is opened up to the time when the valve of the fuel supplying nozzle is closed, is less than the quantity indicated on the indicator by the quantity of fuel which is required to fill the empty part of the pipe arrangement and the hose at the start of the fuel supplying operation in the normal fuel supplying mode.
In a case where the fuel supplying operation is carried out in the preset fuel supplying mode for two successive fuel supplying operations, the quantity of fuel required to fill the empty part of the pipe arrangement and the hose at the start of the latter of the two successive fuel supplying operations is the same as the quantity of fuel which flows out of the fuel supplying nozzle at the completion of this latter fuel supplying operation. In other words, the quantity of fuel which is actually supplied, coincides with the quantity of supplied fuel which is indicated on the indicator. On the other hand, when the previous fuel supplying operation is carried out in the normal fuel supplying mode and the fuel supplying operation is now to be carried out in the preset fuel supplying mode, the actual quantity of fuel which is supplied from the time when the valve of the fuel supplying nozzle is opened up to the time when the valve of the fuel supplying nozzle is closed, is more than the quantity indicated on the indicator by the quantity of fuel which flows out of a part of the pipe arrangement and the hose at the completion of the fuel supplying operation in the preset fuel supplying mode.